Cooling system for vehicle battery pack containing double filter device

ABSTRACT

Disclosed herein is a cooling system for vehicle battery packs, including a double filter device mounted at an air inlet part, through which air for cooling the battery pack is introduced from the outside and/or the inside of the vehicle. The double filter includes a pre-filter having relatively large air holes, the pre-filter having high frequency of replacement, and a medium filter having relatively small air holes, the medium filter having low frequency of replacement. The pre-filter is located before the medium filter in the direction in which the air is introduced. Consequently, dust is removed from air, and therefore, the cooling efficiency of the battery pack is increased. In a preferred structure, metal dust is also effectively removed by the magnetic force applied to the medium filter. Consequently, the malfunction or short circuits of the battery pack are prevented. Also, air surrounding the battery pack is directly introduced through the through-type intake ports without passing through any pipe-shaped intake duct. Consequently, generation of noise, which is a problem caused when air in the cabin is used, and backward flow of flames and toxic gas, which are generated during a fire, are prevented. Furthermore, the battery pack is constructed in a compact structure.

FIELD OF THE INVENTION

The present invention relates to a cooling system for vehicle batterypacks, which are used as a power source for electric vehicles and hybridelectric vehicles, and, more particularly, to a cooling system forvehicle battery packs, including a pre-filter having high frequency ofreplacement and a medium filter having low frequency of replacement,which are successively mounted at an air inlet part, through which airfor cooling the battery pack is introduced from the outside or theinside of the vehicle, thereby effectively removing dust from the air,and therefore, preventing reduction of the cooling efficiency due toexcessive accumulation of the dust, and preventing the malfunction orshort circuits of the battery pack due to contamination of an electricalconnecting part and a circuit board.

BACKGROUND OF THE INVENTION

One of the biggest problems caused from vehicles using fossil fuel, suchas gasoline and diesel oil, is creation of air pollution. A technologyof using a secondary battery, which can be charged and discharged, as apower source for vehicles has attracted considerable attention as onemethod of solving the above-mentioned problem. As a result, electricvehicles (EV), which are operated using only a battery, and hybridelectric vehicles (HEV), which jointly use a battery and a conventionalengine, have been developed. Some of the electric vehicles and thehybrid electric vehicles are now being commercially used. A nickel-metalhydride (Ni-MH) secondary battery has been mainly used as the powersource for the electric vehicles (EV) and the hybrid electric vehicles(HEV). In recent years, however, the use of a lithium-ion secondarybattery has been attempted.

High output and large capacity are needed for such a secondary batteryto be used as the power source for the electric vehicles (EV) and thehybrid electric vehicles (HEV). For this reason, a plurality ofsmall-sized secondary batteries (unit cells) are connected in series orin parallel with each other so as to construct a battery module, and aplurality of battery modules are connected in parallel or in series witheach other so as to construct a battery pack.

In such a high-output, large-capacity secondary battery, however, alarge amount of heat is generated from the unit cells during the chargeand the discharge of the unit cells. When the heat generated from theunit cells during the charge and the discharge of the unit cells is noteffectively removed, heat is accumulated in the unit cells with theresult that the unit cells are degraded. Consequently, it is necessaryto provide a cooling system for vehicle battery packs, which arehigh-output, large-capacity secondary batteries.

Generally, a cooling system for vehicle battery packs is constructed inan air-cooling structure using air as a coolant. In the air-coolingstructure, air outside or inside the vehicle is introduced to cool thebattery pack, and is then discharged out of the vehicle. For example,the cooling system may be constructed in a structure in which an airinlet part, through which air is introduced from a specific regionoutside or inside the vehicle, and an air outlet part, through which theair having passed through the battery pack, which has been heated, isdischarged out of the vehicle, are mounted at a housing (a case), whichsurrounds the outer surface of the battery pack, and air is circulatedby the driving force of a cooling fan such that the battery pack can becooled by the circulated air.

In the case that air outside the vehicle is used as air for cooling thebattery pack, it is necessary to control the temperature and thehumidity of the air. Consequently, it is preferable to use air insidethe vehicle, the temperature and the humidity of which are controlled ata specific level.

The air inside the vehicle, as well as the air outside the vehicle,contains fine dust, although there is a little difference between them.Such dust may cause a serious problem especially in a fuel cell, whichuses air as one of material components for battery operation. For thisreason, U.S. Unexamined Patent Publication No. 2005-8912 and JapaneseUnexamined Patent Publication No. 2004-273311 disclose technologies foreffectively removing dust by means of a filter mounted at an air supplyunit of a fuel cell.

As previously described, air is used to cool the secondary battery pack.Consequently, seriousness of problems due to dust in the case of thebattery pack is lower than that in the case of the fuel cell. However,when such fine dust is introduced into the battery pack along with theair, and, as a result, the dust is excessively accumulated on unit cellsof the battery pack, the cooling efficiency is decreased. Furthermore,when metal dust component among the fine dust is accumulated on anelectrical connecting part and a circuit board of the battery pack, themalfunction or short circuits of the battery pack may be caused.

Consequently, Korean Registered Patent No. 494936 discloses a technologyfor removing dust by means of a filter mounted at an air inlet part ofthe battery pack, and Korean Registered Patent No. 202509 discloses atechnology for removing dust and moisture by means of a filter mountedat the rear of a cooling fan of the battery pack.

The above-mentioned patents disclose the provision of the filter forremoving the dust. However, the detailed construction of the filter isnot disclosed in the patents. It can be understood from the review ofthe patent specifications that a single filter is mounted to removedust. In this case, various-sized dust is filtered by the single filterwith the result that the filter replacing cycle is very short. Also, anexpensive filter is needed to filter fine dust. Especially, it isdifficult to remove metal dust, which may cause the malfunction or shortcircuits of the battery pack.

Meanwhile, the vehicle battery pack must be mounted in a restrictedspace in the vehicle, and therefore, it is preferable that the vehiclebattery pack be constructed in a compact structure. The size of thevehicle battery pack is decided depending upon the size of the batterymodule, which is constructed by stacking unit cells one on another, andthe size of the cooling system, which covers the outer surface of thebattery pack. In connection with this case, the above-mentioned priorarts essentially include an intake duct for introducing air from theoutside of the vehicle or the cabin into the battery pack and an exhaustduct for discharging the air having passed through the battery pack,which has been heated, out of the vehicle. These ducts have apredetermined size, and therefore, the ducts serve as a principal factordeciding the size of the battery pack based on the cooling system forthe battery module with the same condition.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made to solve theabove-mentioned problems, and other technical problems that have yet tobe resolved.

Specifically, it is a first object of the present invention to provide acooling system for vehicle battery packs that is capable of improvingthe cooling efficiency of the battery pack through the use of a doublefilter device that can filter fine dust contained in air.

It is a second object of the present invention to provide a coolingsystem for vehicle battery packs that is capable of effectivelyfiltering metal dust contained in air, thereby greatly reducing apossibility of the malfunction or short circuits of the battery pack.

It is a third object of the present invention to provide a coolingsystem for vehicle battery packs that uses air existing at a regionaround the battery pack as a coolant in addition to the use of thedouble filter device and constructed such that air having passed throughthe battery pack, which has been heated, is discharged into an internalspace of the vehicle, in which a possibility of air to be recirculatedto the region around the battery pack is low, whereby the temperatureand the humidity of the air is easily controlled as compared to the casethat air outside the battery pack is used as the coolant, generation ofnoise, which is a problem caused when air in a cabin of the vehicle isused, and backward flow of flames and toxic gas, which are generatedduring a fire, are prevented, and the cooling efficiency of the batterypack is increased without using any pipe-shaped intake duct.

In accordance with the present invention, the above and other objectscan be accomplished by the provision of a cooling system for vehiclebattery packs, including a double filter device mounted at an air inletpart, through which air for cooling the battery pack is introduced fromthe outside and/or the inside of the vehicle, wherein the double filtercomprises: a pre-filter having relatively large air holes, thepre-filter having high frequency of replacement; and a medium filterhaving relatively small air holes, the medium filter having lowfrequency of replacement, the pre-filter being located before the mediumfilter in the direction in which the air is introduced.

The cooling system for vehicle battery packs according to the presentinvention includes the double filter device comprising the pre-filterand the medium filter. The pre-filter, which is relatively inexpensiveand has the relatively large air holes, is replaced with high frequency.Consequently, the replacing cycle of the double filter device isextended, and therefore, the operation costs of the cooling system arereduced.

The replacing frequency and the size of air holes for the pre-filter arerelative to the replacing frequency and the size of air holes for themedium filter. Also, the pre-filter is disposed before the medium filtersuch that large-sized dust can be filtered by the pre-filter. As aresult, the replacing cycle of the medium filter is further extended.

In a preferred embodiment, a magnetic force may be applied to thefilters such that metal dust can be effectively collected by thefilters. The magnetic force may be generated from a permanent magnet oran electromagnet, although the present invention is not limited to thepermanent magnet or the electromagnet. Generally, the metal dust hasvery small sizes. Consequently, it is necessary to use a filter havingvery small air holes so as to effectively remove the metal dust.However, the filter having very small air holes is very expensive.Furthermore, the flow speed of air is decreased when the filter havingvery small air holes is used, and therefore, the cooling efficiency ofthe battery pack is decreased. On the other hand, when even a smallamount of metal dust is introduced to an electrically connecting part ora circuit board of the battery pack, the malfunction or short circuitsof the battery pack may be caused.

Consequently, in a preferred embodiment of the present invention, themetal dust is removed by the magnetic force applied to the filters,whereby the above-mentioned problems are solved. The magnetic force maybe selectively applied to the pre-filter or the medium filter.Alternatively, the magnetic force may be selectively applied to both thepre-filter and the medium filter.

The magnetic force for collecting the metal dust may be applied to aregion where the filters are not mounted, for example, to an arbitraryregion of the intake duct. However, high magnetic force is required toseparate metal dust from air introduced to cool the battery pack becausethe flow speed of the air is high in the intake duct, which isconstructed in a hollow structure. In the structure the magnetic forceis applied to the pre-filter and/or the medium filter according to thepresent invention, on the other hand, the flow speed of the metal dustis reduced while the metal dust collides with filtering nets of thefilters. Consequently, it is possible to effectively collect the metaldust although the magnetic force is small. Furthermore, the collectedmetal dust sticks to the filtering nets of the filters together withother kinds of dust, and therefore, a possibility of the metal dust tobe separated from the filters and be introduced into the battery pack islow.

The material for the pre-filter and the medium filter is notparticularly restricted so long as the pre-filter and the medium filterhave pluralities of air holes, through which air can pass, under theabove-defined conditions. For example, the pre-filter and the mediumfilter may be made of non-woven cloth. In the structure in which themagnetic force is applied to the filters as described above, thepre-filter and/or the medium filter may be partially or entirely made ofa conductive material so as to increase the collecting efficiency.

The location of the air inlet part, where the double filter device ismounted, is not particularly restricted so long as the air inlet part isa part of the cooling system that introduces cooling air into thebattery pack from the outside and/or the inside of the vehicle. Forexample, the double filter device may be mounted to an arbitraryposition of the intake duct, which is a pipe-shaped member.

In a preferred embodiment, the cooling system may be constructed suchthat air existing inside the vehicle at a region around the battery packisolated from a cabin of the vehicle is directly introduced into thebattery pack through through-type intake ports without passing through apipe-shaped intake duct, and the air having passed through the batterypack, which has been heated, is discharged through an exhaust ductconnected to an internal space of the vehicle, in which a possibility ofair to be recirculated to the region around the battery pack is low,whereby the total size of the cooling system is further decreased. Inthis case, the double filter device may be mounted at the front or therear of the intake ports. According to circumstances, the pre-filter maybe mounted at the front of the intake ports, and the medium filter maybe mounted at the rear of the intake ports.

In the cooling system with the above-stated construction, air existingat the region around the battery pack is used as a coolant, and the airis directly introduced into the battery pack through the through-typeintake ports. Consequently, it is possible to cool the battery packwithout using the pipe-shaped intake duct, which is bulky, andtherefore, the total size of the cooling system is further decreased.

In a preferred embodiment, the cooling system comprises: a closed typehousing for surrounding the outer surface of the battery pack, whichincludes unit cells; a plurality of intake ports formed in the housingat regions corresponding to the unit cells, the double filter devicebeing mounted at the front or the rear of the intake ports; an exhaustduct connected to the housing at a region opposite to the intake ports;and a cooling fan mounted to the exhaust duct.

In the above-described construction, the air pressure inside the housingis reduced due to the operation of the cooling fan, and therefore, airexisting at the region around the battery pack is introduced into thehousing through the intake ports so as to compensate for the reduced airpressure. The intake ports are formed in the housing in the shape of athrough-hole. Consequently, an intake duct, which is necessary for theprior arts, is not needed, and therefore, the battery pack can bemanufactured in a compact structure.

The battery pack is mounted in a specific region isolated from the cabinin consideration of various factors, such as the safety and theoperating efficiency, of the vehicle. For example, the battery pack maybe mounted in a trunk, which is located at the rear of the vehicle.According to the design of the vehicle, the battery pack mountingregion, in which the battery pack is mounted, may be constructed in afully isolated structure, in which the flow of air from the cabin isfully interrupted, or in a partially isolated structure, in which asmall amount of air is allowed to flow. As a result of experiments, theinventors of the present application have confirmed that, even when thebattery pack mounting space is completely isolated from the cabin of thevehicle, a specific amount of air flows between the inside and theoutside of the battery pack mounting space due to the structure of thevehicle, and this air flow is sufficient for cooling the battery pack.Especially, the air flow at the region around the battery pack isfurther increased as a result of the forced discharge of air performedby the cooling fan.

According to the present invention, the air having passed through thebattery pack, which has been heated, is discharged into the internalspace of the vehicle, in which a possibility of air to be recirculatedto the region around the battery pack is low. As a typical example, theinternal space of the vehicle may be a space defined between an innerpanel and an outer panel of the vehicle. Generally, panels are attachedto the inner and outer parts of the vehicle on a frame of the vehicle,which provides mechanical strength, whereby the vehicle is formed in apredetermined shape. Consequently, a specific space is defined betweenthe inner panel and the outer panel of the vehicle. This specific spaceis provided at the opposite side parts, the front part, and the rearpart of the vehicle. Also, the specific space directly or indirectlycommunicates with the outside and/or the inside of the vehicle.

In a preferred embodiment, the exhaust duct of the cooling system isconnected to the space defined between the inner panel and the outerpanel of the vehicle, and therefore, the air having passed through thebattery pack, which has been heated, is discharged into theabove-described space, where some of the air is completely dischargedout of the vehicle, and the remaining of the air is recirculated intothe vehicle. For the air recirculated into the vehicle, the air iscooled again while the air passes through the space. Consequently, ithas been confirmed that the air returned to the region around thebattery pack has conditions suitable for cooling.

The battery pack according to the present invention may be constructedwith a battery module having unit cells, which are mechanically coupledand electrically connected with each other in various forms. In apreferred embodiment, the battery pack may be manufactured with abattery module constructed by mounting one or more plate-shaped unitcells in a cartridge and successively stacking a plurality ofcartridges. A typical example of such a battery module is disclosed inKorean Patent Application No. 2004-111699, which has been filed in thename of the applicant of the present patent application. The disclosureof the above-mentioned patent application is hereby incorporated byreference as if fully set forth herein.

The unit cells are not particularly restricted so long as the unit cellsare batteries that can be charged and discharged. For example, each ofthe unit cells is a secondary battery including cathodes, anodes,separators, and an electrolyte mounted in a container, which ishermetically sealed in a structure in which the charge and the dischargeof each unit cell is possible. Preferably, the unit cells may belithium-ion secondary batteries, lithium-ion polymer secondarybatteries, or nickel-metal hydride batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a typical view illustrating the structure of a cooling systemfor vehicle battery packs according to a preferred embodiment of thepresent invention;

FIGS. 2 and 3 are perspective views typically illustrating a coolingsystem for vehicle battery packs according to another preferredembodiment of the present invention; and

FIG. 4 is an enlarged see-through view of the part A shown in FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings. It should be noted,however, that the scope of the present invention is not limited by theillustrated embodiments.

FIG. 1 is a typical view illustrating the structure of a cooling systemfor vehicle battery packs according to a preferred embodiment of thepresent invention.

Referring to FIG. 1, the cooling system 100 comprises a front air inletpart 110, through which air is introduced toward a battery pack 200including a plurality of unit cells 210, a rear air outlet part 120,through which the air having passed through the battery pack 200, whichhas been heated, is discharged, and a cooling fan 130 for driving air tobe introduced and discharged.

At the air inlet part 110 is mounted a double filter device 300comprising a pre-filter 310 having relatively large air holes and amedium filter 320 having relatively small air holes. A magnet 330 ismounted around the medium filter 320 such that a magnetic force can beapplied to the medium filter 320.

Consequently, when air is introduced into the cooling system through theair inlet part 110 by the driving force of the cooling fan 130,large-sized dust in the air is filtered by the pre-filter 310, andsmall-sized dust and metal dust are collected by the medium filter 320.As a result, only air containing no dust therein passes through thebattery pack 200, whereby the battery pack 200 is cooled.

FIGS. 2 and 3 are perspective views typically illustrating a coolingsystem for vehicle battery packs according to another preferredembodiment of the present invention.

Referring to these drawings, the cooling system 100 includes a housing140, which covers the outer surface of a battery pack (not shown), acooling fan 130, and an exhaust duct 150. The housing 140 is closedexcept for the front surface thereof, at which through-type intake ports142 are formed, and the rear surface thereof, to which a pair of exhaustports 152 are connected.

Each intake port 142 is constructed in the shape of a slit, whichcorresponds to each plate-shaped unit cell of the battery pack. In thisembodiment, a plurality of intake ports 142 are provided incorrespondence to the respective unit cells. Consequently, air isintroduced through the intake ports 142 for the respective unit cells,and passes through the battery pack approximately in a straight line,with the result that the cooling efficiency of the cooling system isvery high. Also, the upper part of each intake port 142 is constructedin a skirt structure, by which foreign matter is prevented from beingintroduced into each intake port 142 from above. Consequently, asindicated by an arrow shown in FIG. 2, the air is introduced into theintake ports 142 while the air is slightly inclined upward.

In order to remove dust contained in the air introduced into the intakeports 142 in spite of the upper skirt structure, a double filter deviceis mounted at the front and/or the rear of the intake ports 142. Thedouble filter device is shown in FIG. 4, which is an enlargedsee-through view of the part A shown in FIG. 2. Referring to FIG. 4, apre-filter 310 and a medium filter 320 are successively mounted at therear of the slit-type intake ports 142, each of which has a skirt formedat the upper part thereof, while the pre-filter 310 and the mediumfilter 320 are in tight contact with each other. Each intake port 210 isformed generally in the shape of a through-hole. Air surrounding thebattery pack is directly introduced through the intake ports 210, andtherefore, any additional intake duct is not required.

Referring back to FIGS. 2 and 3, the battery pack may be preferablymounted in a trunk of the vehicle or the rear part of a rear seat of thevehicle. A lower plate of the vehicle is constructed generally in a bentstructure to increase the structural strength of the vehicle.Consequently, in the case that, as shown in FIG. 2, a base plate 220 ofthe battery pack is constructed in a bent structure corresponding to thebent structure of the lower plate of the vehicle, it is possible tostably mount the battery pack and to further lower the height at whichthe battery pack is mounted. As shown in FIG. 2, a lower end 144 of thehousing 140, which is coupled to the base plate 500 of the battery pack,is also constructed in a bent structure. Consequently, the height atwhich the cooling system 100 is mounted is further lowered. Preferably,the base plate 220 is made of an insulating material, and therefore, thepossibility of short circuits of the battery pack with respect to thevehicle is further decreased.

At the rear surface of the housing 140, which is opposite to the intakeports 142, are formed two exhaust holes 146, which are connected to theexhaust ports 152 of the exhaust duct 150. FIG. 3 shows a process ofconnecting the exhaust ports 152 of the exhaust duct 150 to the exhaustholes 146 of the housing 140.

The cooling fan 130, which is mounted on the exhaust duct 150, providesa driving force, by which air surrounding the battery pack is introducedinto the battery pack through the intake ports 142, cools the batterypack, and is discharged from the battery pack through the exhaust duct150. The exhaust duct 150 is connected to a space defined between anouter panel and an inner panel of the vehicle, as shown in FIG. 1.

The construction of the battery pack will be further described below.

At the right side of the battery pack is located a junction module 230for withdrawing power from the battery pack or interrupting thewithdrawal of power from the battery pack. At the left side of thebattery pack is located a battery management system (BMS) module 240 formonitoring temperature of the battery pack and voltages of the unitcells. Since the junction module 230 and the BMS module 240 are locatedat the opposite sides of a battery module comprising the unit cells, anair flow channel for cooling the unit cells is formed in a straight linehaving the minimum distance, and the total height of the battery pack isgreatly reduced.

The BMS module 240 serves to transmit the monitored information to anoperation system of the vehicle. According to circumstances, the BMSmodule 240 may be constructed such that the BMS module 240 can controlthe operation of the battery pack according to the monitoredinformation. Consequently, the cooling fan 130, which controls thetemperatures of the unit cells, may be constructed such that theoperation of the cooling fan 130 can be automatically controlled by theBMS module 240.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

As apparent from the above description, the double filter device, whichcomprises the pre-filter and the medium filter, is mounted at the airinlet part of the cooling system for battery packs according to thepresent invention. Consequently, dust is removed from air, andtherefore, the cooling efficiency of the battery pack is increased. In apreferred structure, metal dust is also effectively removed by themagnetic force applied to the medium filter. Consequently, themalfunction or short circuits of the battery pack are prevented. Inanother preferred structure, air surrounding the battery pack isdirectly introduced through the through-type intake ports withoutpassing through any pipe-shaped intake duct. Consequently, generation ofnoise, which is a problem caused when air in the cabin is used, andbackward flow of flames and toxic gas, which are generated during afire, are prevented. Furthermore, the battery pack is constructed in acompact structure.

The cooling system according to the present invention is applicable to abattery pack for various kinds of vehicles, such as electric vehiclesand hybrid electric vehicles. Especially, the cooling system accordingto the present invention is preferably applicable to a battery pack forhybrid electric vehicles.

1. A cooling system for vehicle battery packs, including a double filterdevice mounted at an air inlet part, through which air for cooling thebattery pack is introduced from the outside and/or the inside of thevehicle, wherein the double filter comprises: a pre-filter havingrelatively large air holes, the pre-filter having high frequency ofreplacement; and a medium filter having relatively small air holes, themedium filter having low frequency of replacement, the pre-filter beinglocated before the medium filter in the direction in which the air isintroduced.
 2. The cooling system according to claim 1, wherein amagnetic force is applied to the filters such that metal dust containedin the air can be effectively collected by the filters.
 3. The coolingsystem according to claim 2, wherein the filters are partially orentirely made of a conductive material.
 4. The cooling system accordingto claim 1, wherein the cooling system is constructed such that airexisting inside the vehicle at a region around the battery pack isolatedfrom a cabin of the vehicle is directly introduced into the battery packthrough through-type intake ports without passing through a pipe-shapedintake duct, and the air having passed through the battery pack, whichhas been heated, is discharged through an exhaust duct connected to aninternal space of the vehicle, in which a possibility of air to berecirculated to the region around the battery pack is low, and thedouble filter device is mounted at the front or the rear of the intakeports.
 5. The cooling system according to claim 4, wherein the coolingsystem comprises: a closed type housing for surrounding the outersurface of the battery pack, which includes unit cells; a plurality ofintake ports formed in the housing at regions corresponding to the unitcells, the double filter device being mounted at the front or the rearof the intake ports; an exhaust duct connected to the housing at aregion opposite to the intake ports; and a cooling fan mounted to theexhaust duct.
 6. The cooling system according to claim 4, wherein thebattery pack is mounted in a trunk, which is located at the rear of thevehicle.
 7. The cooling system according to claim 4, wherein theinternal space of the vehicle, to which the exhaust duct is connected,is a space defined between an inner panel and an outer panel of thevehicle.
 8. The cooling system according to claim 5, wherein each of theintake ports is constructed in the shape of a slit, which corresponds toeach plate-shaped unit cell of the battery pack, and the intake portsare located in correspondence to the respective unit cells.
 9. Thecooling system according to claim 5, wherein the upper part of eachintake port is constructed in a skirt structure, by which theintroduction of foreign matter is prevented.
 10. The cooling systemaccording to claim 5, wherein the pre-filter and the medium filter aresuccessively mounted at the rear of the intake ports while thepre-filter and the medium filter are in tight contact with each other.